The invention relates to printing systems, and more particularly, to color printing systems.
Photosensitive elements, which can be used in image-reproduction processes, are well known in the graphics arts industry. Such elements are usually exposed to actinic radiation through an image-bearing transparency, such as a color separation transparency, to produce an image which is either a positive or negative with respect to the transparency used.
Photosensitive elements are widely used in off-press color proofing to simulate the images produced by printing. In a surprint proof, all of the colored images are superimposed, by, for example, multiple exposure, lamination, or transfer, onto a single support. Unlike an overlay proof, the colored images cannot be separated and viewed individually.
Various processes for producing copies of images involving photopolymerization and thermal transfer techniques are known. Generally, in these processes, a photopolymerizable layer coated on a suitable support is imagewise exposed to a photographic transparency. The surface of the exposed layer is then pressed into contact with the image receptive surface of a separate element, and at least one of the elements is heated to a temperature above the transfer temperature of the unexposed portions of the layer. The two elements are then separated, whereby the thermally transferable, unexposed, image areas of the composite, transfer to the image receptive element. If the element is not precolored, the tacky, unexposed image may now be selectively colored with a desired toner. All of these processes necessitate the use of specially treated final receptor sheets and are not applicable for obtaining a color proofing image on a paper stock. If the element is precolored, flexibility in the choice of colors is limited because preparation of the precolored elements in all the desired colors is not economically feasible. Toning provides greater color flexibility.
U.S. Pat. No. 5,534,387 discloses a process for forming a colored image, said process comprising, in order: applying at least one aqueous permeable colorant-containing composition to a photosensitive element comprising, in order, a carrier element having a release surface, said carrier element being resistant to aqueous liquid development, a first adhesive layer, an unpigmented, first photosensitive layer consisting essentially of an aqueous liquid developable photosensitive composition, wherein the aqueous permeable colorant-containing composition is in contact with the first photosensitive layer, wherein the aqueous permeable colorant-containing composition is applied the unpigmented photosensitive composition. After imagewise exposing to actinic radiation, the photosensitive element having applied thereon the permeable colorant-containing composition results in imagewise exposed and unexposed regions in the unpigmented, first photosensitive layer and the overlying permeable colorant-containing composition. The element is then developed thereby removing either the imagewise exposed or imagewise unexposed regions, to produce a first colored pattern. A transfer element having a release surface is then laminated to the element having the first colored pattern, wherein the release surface is adjacent to the first colored pattern. The carrier element is then removed, revealing the adhesive layer. This element is then laminated to the permanent substrate and the transfer element having a release surface is peeled off to leave a single color image on the permanent substrate. A process for forming a multicolor image is also disclosed. This process provides the color flexibility, but the time needed to prepare these proofs is longer than that required to form a laser induced thermal image. Further, because this is an analog process, it requires the use of separation transparencies that require repeating each time a color change is desired.
U.S. Pat. No. 6,165,654 (Taylor et al.) discloses a combination digital/analog color proofing method having the steps of: digitally forming a color thermal image on a receiver element comprising a receiver support and an image receiving layer; laminating the digitally formed image with a film comprising a support having a release surface and a thermoplastic polymer layer; removing the support thereby revealing the thermoplastic polymer layer, and leaving the digitally formed image encased between the image receiving layer and the thermoplastic polymer layer; and laminating an analog color image to the revealed thermoplastic polymer layer to create a color proof having at least two color images.
The present invention relates to a hybrid method for forming a color image proof wherein an analog color image can be formed directly on a digital color image.
A need exists for combining the high resolution and speed afforded by laser induced processes with the color versatility afforded by analog systems. Further, there exists a need for a method/system for generating a digital color image utilizing more than just laser induced transfer systems in combination with the color versatility of analog systems. Additionally, there exists a need for a streamlined hybrid method for generating a combination digital/analog color image, wherein each of the digital color image and analog color image are not generated separately.
In accordance with the present invention, the invention is directed to a method for forming a hybrid digital/analog color image that includes generating a digital color image on a substrate, assembling an analog receiver material in intimate contact with the substrate bearing the digital color image, coating a photopolymerizable analog color material on the analog receiver material, imagewise exposing the photopolymerizable analog color material to radiation, and processing the exposed photopolymerizable analog color material to form a hybrid digital/analog image.
In another embodiment, the invention is directed to a method for forming a hybrid digital/analog color image comprising generating a digital color image on a substrate and assembling an analog receiver material in intimate contact with the substrate bearing the digital color image. The analog receiver material is coated with a photopolymerizable analog color material prior to assembly. The method also includes imagewise exposing the photopolymerizable analog color material to radiation and processing the exposed photopolymerizable analog color material to form a hybrid digital/analog image.
In the methods of the present invention, a digital color image can be generated by a technique selected from the group consisting of inkjet, thermography, electrophotography, electrography, laser induced transfer, and a combination thereof. Preferably, the laser induced transfer method comprises a transfer method selected from the group consisting of dye sublimation, ablation, melt transfer, and film transfer.
In one embodiment, the method of the present invention includes generating a digital color image by assembling a digital donor element comprising a colorant in intimate contact with a digital receiver element, exposing the assembly to radiation to transfer at least a portion of the colorant of the digital donor element to the digital receiver element, and separating the digital donor element from the digital receiver element, leaving a color image residing on the digital receiver element. The steps of assembling, exposing and separating form a cycle that can be repeated at least once, wherein a different donor element comprising a different colorant is used in each repetition of the cycle but the same digital receiver element is used in each repetition of the cycle.
According to the methods of the present invention, the methods may further include coupling the hybrid digital/analog image to a final receptor and removing a digital receiver element from the digitally generated color image to form a hybrid digital/analog color proof.
Also, the methods may further include, for example, assembling a second analog receiver material in intimate contact with the hybrid digital/analog image, coating a second photopolymerizable analog color material on the receiver element, and repeating the imagewise exposing and processing steps to generate a hybrid digital/analog color image having two different analog color images thereon.
The invention may offer many advantages. Analog techniques may advantageously offer a wide range of colors, and digital techniques may advantageously offer easy storage and manipulation of image data. The invention may further enhance registration of digital and analog images.